Mulgrew and Brown both came off during Celtic's 2-1 defeat by Benfica in Lisbon on Tuesday night.

"Thomas Rogne is not far away," Lennon said. "Scott, the problem is the stomach and hip area seems to flare up every now and then. That wasn't the problem on Tuesday, he was cramping up with the lack of training he has had, to rest between matches.

"Joe Ledley is starting to show similar symptoms to Scott so we will have to be careful with that.

"Charlie was not feeling very well on Tuesday and may miss the Inverness game."

Lennon revealed he would rest players ahead of the Spartak game after feeling fatigue was a problem in Portugal during Celtic's 24th competitive match of the season.

"Charlie has played in practically all of them, as has Fraser (Forster)," Lennon said.

"A culmination of things, travelling, going away with international teams as well, it begins to take its toll.

"I'm going to have to use the squad for these upcoming games. We need players who haven't played as much as they would like to really come to the fore and make sure our league form is consistent, so we go into the Spartak game ready to go."